import java.util.Scanner;

public class code01 {
    //数组
    public static void main(String[] args) {
        int []data = new int[200];
        for(int i=0;i<200;i++) {
            data[i] = 4*i+6;
        }
        Scanner scan = new Scanner(System.in);
        int x = scan.nextInt();
        for(int i=0;i<200;i++) {
            if(data[i]==x) {
                System.out.print(i);
                break;//记得break
            }

        }
    }

}

